Sow productivity has traditionally been defined as the number of progeny pigs weaned per sow per year. However, the length of time that sows remain productive within commercial operations also plays a major factor in their profitability and economic success. Producers are financially rewarded for having sows with an improved productive lifetime because the initial cost of the replacement gilt and associated development expenses to be spread across a greater number of piglets produced during the sow's lifetime.
Current sow culling rates are excessive and often sows are removed from the breeding population before reaching their breakeven parity. This situation can affect overall profitability. Reasons for culling sows can be attributed to genetics, reproduction, nutrition, environment, and management. However, premature culling of breeding sows tends to fall into two distinct categories:                Very early culling of gilts and parity 1 sows on the basis of reproductive failure and locomotor problems.        Culling around parities 3-5 for poor reproductive performance.        
Therefore, reproductive failure is accepted to be the largest reason for the culling of primiparous sows.
Sow productive lifetime or length of productive life is typically measured several ways, including days of age from birth to culling, life from entry into the breeding population through culling, and the number of successful parities completed. Currently, the Australian industry average is predicted to be 30-40 pigs weaned/lifetime which is well below the potential to produce at least 80-90 pigs weaned per sow per lifetime. Similar poor sow reproductive performance is also reported in most other major pig producing countries. Therefore, pig producers are constantly looking for ways to increase sow performance and productive life.
For many years it has been thought by most within the research community that the limitation to improved reproduction is simply a matter of improving the implementation of existing knowledge to producers. However, with national herd statistics showing that reproduction is not improving, pig producers are highlighting that this approach must be combined with both large scale studies that report on longevity and research into the fundamental nutritional and management requirements, in particular because of today's genetically lean genotypes.
Studies have shown that modification of the gilt's fat reserves as she enters the breeding population through protein restriction or increased feeding levels rarely demonstrates an improvement in reproductive performance over several parities. Likewise, no improvement in reproductive performance has been seen by increasing fatness in sows fed high energy diets during successive pregnancies. Increasing protein intake in gestation and lactation has also been recently studied in young sows. While litter size born subsequent to sows being fed high protein diets during the first lactation was positively correlated with lactation lysine intake, no benefit of high protein intake on weaning to conception interval was observed.
Accordingly, there exists an ongoing need to develop new and effective methods for increasing reproductive performance in sows and therefore sow lifetime productivity.